Concentrations and loads of pcbs and oc pesticides in the urbanized guadalupe river watershed
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Item #2. Concentrations and loads of PCBs and OC pesticides in the urbanized Guadalupe River watershed. Presented to: RMP Sources, Pathways, and Loadings Workgroup May 22, 2007. Jon Leatherbarrow San Francisco Estuary Institute, Oakland, CA UC Davis, Civil & Environmental Engineering, Davis, CA.

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Concentrations and loads of PCBs and OC pesticides in the urbanized Guadalupe River watershed

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Item #2

Concentrations and loads of PCBs and OC pesticides in the urbanized Guadalupe River watershed

Presented to:RMP Sources, Pathways, and Loadings WorkgroupMay 22, 2007

Jon LeatherbarrowSan Francisco Estuary Institute, Oakland, CAUC Davis, Civil & Environmental Engineering, Davis, CA

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PCB and OCP use in urban areas

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Legacy contamination in urban environment

  • Areas of heaviest use of PCBs; contaminated areas; continued use and accidental release;

  • Areas of most recent widespread use of many OCPs (e.g., chlordane, dieldrin, HCHs); direct application, release

  • Development and disturbance of former agricultural lands; post World War II and Silicon Valley “boom” in the 1960s

  • Persistence in watershed soils and aquatic sediments due to chemical and physical stability;

  • Continuing local, regional, and global impacts from cycling of contaminant residues through non-point source pollution pathways (i.e., runoff, atmospheric)

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Guadalupe River monitoring approach

  • Sample collection:

    • PCBs(n=72, WY2003-06)

    • OCPs: DDT, HCHs(n=44WY2003-04)

      dieldrin, chlordane

    • Grab samples (WY2003)

    • D-96 sampler (WY2004-06)

  • Sample analysis

    • Laboratory: Axys Analytical Services, Ltd. Sidney, BC

    • Method: HRGC/HRMS, EPA 1668A

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Guadalupe River monitoring results

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Rising stage ●

Falling stage

Base flow ■

Regression: contaminants on SSC

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Annual loading (***preliminary***)

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Estimates from Fikslin and Suk (2003); Foster et al. (2000a,b); Ko and Baker (2004); Leatherbarrow et al. (2005)

Watershed yields: Penta-PCBs

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Rowe et al. (2007) estimate that highlighted watershed yields reported in Delaware River TMDL are atmospherically driven

Watershed yields: Penta-PCBs

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Sum of p,p’-isomers of DDE, DDD, DDT

Sum of chlordane compounds

Watershed yields*: Pesticides


*All yields in ng/m2/day;

Estimates from Foster et al. (2000); Foster et al. (2003); Leatherbarrow et al. (2005)

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Potential sources: PCB congeners

12/16/02 19:55 (GR24)

10/26/04 5:50 (GR310)

10/26/04 7:50 (GR311)

Aroclor 1260

Aroclor 1254

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Potential sources: PCB congeners

Ratio of GR311:GR310

Aroclor 1016

Aroclor 1242

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Penta-PCBs ▼ Hepta-PCBs □

Watershed processing of PCBs

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p,p’-DDT ▼ p,p’-DDD □

Watershed processing of DDT

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Implications of findings: sources

  • Diffuse source distribution in the watershed:

    • Positive linear relationships of contaminants with SSC;

    • Relatively constant PCB congener profile;

  • Gradient in contamination from urban to non-urban areas:

    • Differences in rising and falling stage regressions indicates high SSC-based concentrations likely emanating from lower urban areas compared to upper non-urban areas;

  • Periodic inputs of PCBs from unique sources:

    • Anomalous profiles in some samples;

    • Atmospheric inputs likely discernable in evolving profile patterns;

  • Relatively unweathered sources of pesticides:

    • High percentage of parent DDT material at high flows;

    • Similar increase in technical mixture profiles in other OCPs;

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Implications of findings: loadings

  • Watershed yields consistent with contaminated urban areas:

    • PCB yields above expected yields from atmospheric deposition;

  • Urban influence evident compared to other land uses:

    • Comparison of watershed yields indicates high potential source density in urban areas compared to non-urban areas;

  • Urban runoff contributes to impairment of SF Bay:

    • Mass budget models indicate loading of PCBs and OCPs on the order of 10 kg/yr could significantly delay water quality improvement;

    • PCB TMDL loading target for urban runoff = 2 kg/yr

    • Loads of 0.5-1 kg/yr from Guadalupe, combined with other tributaries, are expected to contribute to prolonged impairment of water quality.

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Information needs

  • Modeling

    • Hydrologic routing: where is the water coming from?

    • Sediment transport: where is the sediment coming from?

    • Contaminant transport: link evolving contaminant profiles to sources of water and sediment.

  • Treatment options

    • Source reconnaissance

    • Structural treatment device placement and optimization

  • Information gathering on other tributaries

    • Monitoring other selected tributaries

    • Extrapolation/modeling methods

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